Brakes - ABS and Traction Control System Description: Overview

Group 34
Brakes

Bulletin Number
34 01 94 (2142)

Woodcliff Lake, NJ
September 1994
Product Engineering

SUBJECT:
Slip Control Systems - Model Year 1994

Situation:

The antilock braking system (ABS), with its ability to minimize skidding when the brakes are applied, has become an essential element in active vehicle safety, and is now installed on all BMW models.

ASC systems are a useful addition to ABS, and improve driving stability and traction by regulating wheelspin when insufficient road surface grip is available.

The sections below describe the revised systems (ABS5/ASC5) from Bosch available on 1994 model-year cars.

These systems represent a further design optimization in terms of function and weight, and also enable the number of different versions to be reduced. From the 1995 model year on, only the systems mentioned above will be installed (with the exception of the 85OCSi, and the Teves System found on E36 models).





The table is a summary of all the systems installed on specific models in the 1994 model year.

ABS 5: Changes compared with 1993 model year:

- Change from 3/3- to 2/2-way control valves with two hydraulic unions and two switching positions.

- Brake force split "black-and-white" in all cases; in other words one circuit to the front wheel brakes, the other to the rear wheel brakes.


ABS/ASC 5: Changes compared with 1993 model year:

- The hydraulic unit has 2/2-way control valves, as in the ABS 5 system.

- The plunger hydraulics with reservoir used on the E31 and E34/M60 with reservoir as an independent component between the hydraulic unit and the rear-wheel brakes are now deleted. Omission of the hydraulic servo circuit simplifies the filling and bleeding procedures.

- On the E34/M50, intake air is regulated at an additional throttle assembly (E31, E341M60: already used on production cars).